A flexible direct current power transmission technology provides an effective solution for large-scale grid connection and consumption of renewable energy, and is widely demanded and has broad application market throughout the world. However, due to lack of a direct current circuit breaker applicable to a high-voltage direct current system, development and construction of a flexible direct current power grid is greatly limited.
Present high-voltage direct current circuit breakers mainly include hybrid direct current circuit breakers, which combine advantages of low running loss of mechanical direct current circuit breakers and quick breaking of solid-state direct current circuit breakers. For example, a hybrid direct current circuit breaker researched and developed by the ABB has high high-voltage technical performance, its rated voltage reaches 200 kV, a breaking time does not exceed 3 ms, and a breaking current reaches 15 kA. However, such a hybrid direct current circuit breaker includes a large number of high-power fully-controlled power electronic devices, and factors of low single-tube withstand voltage, high cost and the like of the high-power fully-controlled power electronic devices make the hybrid direct current circuit breaker expensive.
High-voltage direct current circuit breakers are required to be arranged on both sides of each direct current power transmission line of a flexible direct current power grid to implement quick isolation of a failure line. Therefore, along with continuous enlargement of a transmission scale of the flexible direct current power grid, a number of applied high-voltage direct current circuit breakers is also multiplied, which further increases investment cost of the flexible direct current power grid and is favorable for its development and construction.